Polyalphaolefins (PAOs), Gas-to-Liquid (GTL), Visom, and the like, are important class of lube base stocks with many excellent lubricating properties, including high viscosity index (VI) but have low polarity. This low polarity leads to low solubility and dispersancy for polar additives or sludge generated during service. To compensate for this low polarity, lubricant formulators usually add one or multiple polar co-base stocks such as esters or alkylated naphthalenes. Such polar co-base stocks are often used in PAO formulations at 1 wt %-50 wt % levels to increase the fluid polarity.
Esters and alkylated naphthalene base stocks have many advantages but also have some disadvantages. Alkylated naphthalene is a key component in passenger vehicle lubricants, commercial vehicle lubricants, and industrial products. Alkylated naphthalene is very stable molecule but is not very polar. Esters are polar but potentially hydrolytically unstable. Ideal esters would be those having an ester group at the end of the molecule rather than middle as found in commercial adipate type esters.
There is an interest and opportunities in developing Group V polar base stocks from potentially inexpensive and/or “renewable” feeds based raw materials. For environmental, economical, and regulatory reasons, it is of interest to produce fuels, chemicals, and lube oils from renewable sources of biological origin. Most common biological sources are natural oils, which can be derived from plant sources such as canola oil, castor oil, sunflower seed oil, rapeseed oil, peanut oil, soy bean oil, and tall oil, or derived from animal fats. The basic structural unit of natural oils and fats is a triglyceride, which is an ester of glycerol with three fatty acid molecules represented by the following structure:
wherein R1, R2, and R3 represent C4-C30 hydrocarbon chains.
In the hydrolysis of triglycerides, one obtains glycerol and fatty esters. With recent development in biodiesel production, unsaturated fatty acids and their esters are increasingly available. Use of these molecules as feedstocks would be desirable. Biodiesel (methyl oleate) is produced via the transesterification of seed oils. However, biodiesel has a problem associated with oxidation due to unsaturated double bond in the fatty esters.
Therefore, it would be desirable to take advantage of the renewable feedstocks, thus saving non-renewable petroleum raw materials. Furthermore, there is a need for a process for producing saturated hydrocarbon ester starting materials of biological origin, and to avoid the problem associated with oxidation due to unsaturated double bonds in the fatty esters. There is also a need for Group V base fluids that are high performance base stocks and that differentiate from existing base stocks, e.g., fuel-economy enabling base stocks having low viscosity Kv100 and high viscosity index (VI). There is a further need for polar fluids that provide appropriate solubility and dispersibility for polar additives or sludge generated during service of lubricating oils.
The present disclosure also provides many additional advantages, which shall become apparent as described below.